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TPS82130: TPS82130 outputing a voltage when enable pin is low

Franklin Cooper
Intellectual 2020 points
Part Number: TPS82130

Hi,

I have a design where my on board switch is connected to the positive and negative terminals of my battery. The switch output is connected to the TPS82130SILR enable pin. When the switch is on I want TPS82130SILR to output a voltage. When the switch is off I want TPS82130SILR to not output anything. The battery will output 8.4V max.

On my prototypes initially this works well. However, after several hours of testing TPS82130SILR continues to output a voltage no matter the voltage connected to the enable pin. So even when this pin is grounded directly via a jumper wire the device is still outputting a voltage.

I verified there aren't any shorts between EN and any other neighboring pins on the device. When the switch is set to off there aren't any shorts between EN and the battery positive terminal. When I measure the voltage of the EN pin from a near by via when the switch is off it shows 0V.


What can cause this device to randomly keep outputting the correct voltage irrespective of the voltage on the enable pin?

Highlighting EN pin signal. This signal isn't connected any where else.

  • 0
    TI__Genius 9550 points

    hi,

    I am checking it and will give you feedback on Monday.

  • 0
    TI__Genius 15135 points

    Hi, Cooper

    Need you probe some waveforms by oscilloscope.

    Turn off the swtich, add 0.5A loading at VOUT, probe EN, PG, SS pin voltage.

    Under same condition, probe VOUT and SW voltage(another teminal of inductor).

  • 0 in reply to Zhao Ma
    TI__Intellectual 2020 points

    Hi Zhao,

    The regulator on this board stop working over the weekend. Therefore, I won't be able to run the test you requested. I'm a bit at a loss what can cause this regulator to go from working normally, to ignoring the enable signal to then stop working at all.

    This is the second board that I've had that had the TPS82130 get stuck on the on state. This problem doesn't happen immediately. I'm not sure if this is limited to the two boards or if this is a problem that will impact every board. Any thoughts on what could cause this issue? The customer is planning on building several hundreds of these asap and I would like to root cause the problem before then.

  • 0 in reply to Franklin Cooper
    TI__Genius 15135 points

    Hi, Cooper

    When EN is pull low, IC will shut down, the internal entire circuitry are turned off. I think the output voltage cannot be kept at 5V, it will be discharged by divider resistor slowly if no add loading.

    Comments:

    1. Did you add loading when you found the output keep working issue?

    2. You have to duplicate the issue, and probe my suggested waveforms, then we can debug it.

  • 0 in reply to Zhao Ma
    TI__Intellectual 2020 points

    Hi Zhao,

    1. Yes there is a load.

    2. Ok

    Any initial thoughts on what could be going on?

  • 0 in reply to Franklin Cooper
    TI__Genius 15135 points

    Hi, Sir

    I have a little doubt about the pwer switch, during its turning on and off, it causes noise to EN pin, so please monitor its voltage by oscillascope all the time.  

    Please focous on the duplicating the issue.

    Besides, suggest to add 0.1uF cap for EN pin which can filter noise, it might help to fix this issue.